Why the A?

From what I have read the a/e in the abil/ebil suffix is a particle to ´glue´ the suffix to the root verb (bilmek).

Click here for a lengthy discussion on the a/e part, especially from post 7 onwards.

Manisa Turkish also gives a summary of how to use the abil/ebil suffix here

Thank you

another question please

konuşabiliyorum means i can(am able) to run

if i want to make it in the negative state 

would it be konuşmabiliyorum

or konuşabilmiyorum ?

Neither, the negative ability (cannot) is made by using

-(y)a+ma OR -(y)e +me

konuş + a + ma + iyor + um = konuşamıyorum = I can´t speak .....

click here for a further explanation from Manisa Turkish

while you speak about a ability, you use ´ebilmek/abilmek(can)´.

    affirmative sentence: I can speak English. Ben İngilizce konuşabilirim. (-ir= Simple Present Tens)

    negative setence   : I can´t speak English. Ben İngilizce konuş-a-mam.

We use this in Turkish. Thank you.

while you speak about a ability, you use ´ebilmek/abilmek(can)´.

    affirmative sentence: I can speak English. Ben İngilizce konuşabilirim. (-ir= Simple Present Tens)

    negative setence   : I can´t speak English. Ben İngilizce konuş-a-mam.

We use this in Turkish. Thank you.